1. Field of the Invention
The present invention relates to a method for measuring the fill level of a fluid in a housing by using an ultrasound sensor, in which the measurement is carried out along a measurement path on which there is a reference point, and in which multiple echoes in relation to the signal reflected from the reference point and level echoes in relation to the signal reflected from the fluid level as a result of multiple measurements and located in the time domain of the multiple echoes are generated.
2. Description of Prior Art
Currently in such fill level measurements, ultrasound sensors are employed. These sensors measure the ultrasound propagation time from the sensor as far as a reference point on a measurement path, which is generally a reflector. With the aid of the known path length from the sensor as far as the reference point and the measured propagation time, the speed of sound, for example, is then calculated. It goes without saying that, here, the distance between measuring housing and reference point must be filled with fluid.
In the actual fill level measurement, the ultrasound propagation time between sensor and the fill level is measured. With the aid of the speed of sound determined via the reference measurement described above, the fill level can then be determined in accordance with the simple formula s=t*v.
In the propagation time measurement that is carried out, signal echoes are therefore generated both from the reference point and from the fluid level. Here, multiple echoes are generated in relation to the reference echoes, which means that ping-pong echoes are produced between the transducer of the ultrasound sensor and the reference point. These echoes always follow one another at the same interval according to a multiple of the transducer-reference point path.
Here, the problem arises that the level signal to be measured lies chronologically within the multiple echoes from the reference point. Here, it is not readily possible to distinguish between the various signals (multiple and level echoes), so that, as a result of a lack of an accurate identification of the level echo, it is possible for erroneous measurements to occur.